Aerodynamic noise prediction for long-span bodies

A computational methodology is proposed for aerodynamic noise prediction of long-span bodies at low Mach numbers. The three-dimensional hydrodynamic field is computed by incompressible large eddy simulation, while its two-dimensional acoustic field at zero spanwise wavenumber is solved by the linearized perturbed compressible equations (LPCE). A far-field acoustic pressure is obtained by extrapolating the pressure fluctuations with Kirchhoff method, followed by a three-dimensional correction with Oberai et al.'s formula. The far-field sound pressure level for the long span is then estimated by a correction method, which is formally derived by revisiting the previous works of Kato et al. and Perot et al., along with discussion on finding the spanwise coherence lengths. The accuracy of the present method is assessed for broadband noise (with a broadened tone) from a flow with Re_D = 4.6 × 10⁴ and M = 0.21, past a circular cylinder of 30 cylinder-diameter span. The computed aerodynamic and acoustic results are found in excellent agreement with the experimental measurements.